$-7jkl - 5k - 8l + 3 = 7k - l - 9$ Solve for $j$.
Combine constant terms on the right. $-7jkl - 5k - 8l + {3} = 7k - l - {9}$ $-7jkl - 5k - 8l = 7k - l - {12}$ Combine $l$ terms on the right. $-7jkl - 5k - {8l} = 7k - {l} - 12$ $-7jkl - 5k = 7k + {7l} - 12$ Combine $k$ terms on the right. $-7jkl - {5k} = {7k} + 7l - 12$ $-7jkl = {12k} + 7l - 12$ Isolate $j$ $-{7}j{kl} = 12k + 7l - 12$ $j = \dfrac{ 12k + 7l - 12 }{ -{7kl} }$ Swap the signs so the denominator isn't negative. $j = \dfrac{ -{12}k - {7}l + {12} }{ {7kl} }$